FYI, the new ones are now available. You can add whatever kind of output you want. Two edcor transformers on the output and you've got a great dac.
http://hifimediy.com/?page_id=18&category=7
I was just looking at that today and was about to post... then I remembered "search before posting"...

Which Edcors are you referring to?
These have a spec of 100Hz - 15k, although that is probably at max input voltage.
I've wondered about these differential-output DACs. The datasheets say (the one I looked at anyway) that you do need to treat them as a differential signal, so you have various DACs including DacMagic and miniDSP 2x8 that buffer the differential outputs to get the differential/"balanced" out, then another op-amp to get the single-ended output. On the DM I've read that taking one leg of the balanced out sounds better than the single ended out, altho I never tried it when I had one, nor have I tried it with the miniDSP.